Container with cleavable coating on interior surface



Apnl 16, 1963 c. w. wlLKxNs 3,085,731

CONTAINER WITH CLEAVABLE COATING ON INTERIOR SURFACE Filed June 6, 1956INVENTOR l Www/M ATTORNEY CGNTAINER WHTH CLEAVABLE COA'HNG 0N NTERIQRSURFACE Colbert William Wilkins, lacksonville Beach, Fla., as-

signor, by mesne assignments, to Owens-Illinois Glass Company, Toledo,hio, a corporation of Ohio Filed .lune 6, 1956, Ser. No. 589,809 6Claims. (Cl. 229--3.1)

This invention relates to cleavable release coatings and particularlypertains to coating compositions for application to the inside walls offiber board containers, and to such containers having coatings -on theinner Walls.

A general object of the invention is to provide improved releasecoatings `and coating compositions, and specific objects include theprovision of coatings and coating compositions Which are less costly,which are eifective in decreased thickness, which are highly heatresistant, both in that the coating itself is not adversely affected byhigh temperatures and in that the container itself is protected fromdamage from high temperatures of the contained material by the coating,which do not crack or peel away from the container Wall material, whichare more easily applied to the container Wall material, which permitrolling or stacking of coated material on itself with minimized stickingof the coated face to the next layer of material, which do notundesirably contaminate the product which it is desired to package inthe container, and which cle-ave within the coating to release theproduct from the container.

The invention nds special applicability to the art of packaging asphalt,and other materials which present similar packaging problems, forexample, resins and bitumens generally, latex, and the like, such as maybe termed meltable gummy solids, `and which are ordinarily melted atelevated temperatures for pouring into the containers and thereafterpermitted to cool and solidify.

While fiber board cartons and drums seem presently to offer the mostsatisfactory and economic containers for asphalt and similar products,it will be understood that the coatings of this invention may be used onwooden barrels or on containers made of other materials and of othertypes of construction.

Many release coating mixtures have been heretofore proposed, among whichare, for example, wax emulsions containing, typically, bentonite,emulsifying agents and graphite, and various starch-containing mixtures.The coatings formed of such prior art mixtures, however, have left muchto be desired, in that clays of acceptable quality are expensive, inmost instances considerable thickness of the coating has been necessary,the resistance to cracking and peeling away of the coating has been low,necessitating great care in handling of the coated containers, thecoatings have been ditlicult and expensive to apply and oftenineffective for the intended purpose, or the coating was itselfdestroyed by hot materials o-r proved ineffective to protect thecontainer from damage from hot materials. A particularly diflicultproblem has been the provision of a coating which will stand up andwhich will protect the container when the container is filled with hotdead-level asphalt.

The novel features which are believed to be characterf istie of thisinvention are set forth with particularity in the appended claims. yTheinvention itself, hofwever, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be under.

3,085,731 PatentedA Apr. 16, 1963 stood by reference to the followingydescription taken in connection with the 'accompanying drawing, inwhich:

FIG. l is an isometric view of a container of -a type useful in thisinvention;

FIG. 2 is a fragmentary sectional view -of a portion of a container wallhaving a coating thereon in accord with this invention; and

FIG. 3 is a fragmentary sectional view of a portion of a container wallhaving a double coating thereon in accord With a modification of thisinvention.

As seen in FIG. l, container 1 comprises a kraft fiber box or cartonadapted to contain asphalt or the like. In accord with the invention,the inner walls 2 of the container are coated with a cleavable coating,whereby the container may be torn away from a contained hard block ofasphalt when it is desired to use the asphalt, as at a constructionsite. End Wall top flaps 3 and side wall top aps 4 are also preferablycoated with the cleavable coating.

The container is typically formed of a double wall tluted kraft board 5as seen in FIG. 2 and carries a coating 6 comprising, as later describedin detail, a synthetic resin binder material having small solidparticles dispersed therein. The exposed coating surface 6 hascharacteristic tackiness, at least at elevated temperatures, and bondsor adheres to the material to be contained by the container.

FIG. 3 discloses a modification of the invention wherein solid kraft berboard Wall 7 carries a base or bottom coat 8 of a synthetic plastic inwhich are dispersed small solid particles and, in overlying relation tothe base coat, a top coat 9 of a synthetic resin having an exposedsurface 9 which is presented to the material to be contained in thecontainer yof which the Walls are formed of board 7 L The surface 9 ispreferably non-tacky and hard -at room or atmospheric temperatures, butbecomes tacky at elevated temperatures.

It has been found that certain substances heretofore employed in releasecoating formulations can be profitably employed in the presentinvention, but certain important departures from previous teachings haveresul-ted in a much improved coating, which can be deposited at arate aslow `as six pounds per one-thousand square feet and yet functioneffectively, which is substantially less costly than the most nearlycomparable coating, and which will, in accord with preferred embodimentsof this invention, operate satisfactorily not only to release hotdead-level asphalt poured into the container at about 400 F. but also toprotect the container from damage from the high temperature of thecontained asphalt.

'Either of two systems may :be employed in practicing this invention, asingle coat system, as shown in FIG. 2,' or la double coat system, asshown in FIG. 3. In the former, .a single :coat 6 may be spread by anyof several methods on the surface of the Wall material, Which may be,typically, either double `wall corrugated or solid kraft liber board.The coating material, yas spread, will cornprise a slurry wherein Wateris employed to carry in emulsion a binder material, such as an acrylicresin, and in suspension, small particles of solid materials as furtherexplained hereinafter. The material may also 'comprise subsidiary`chemicals for perform-ing, for example, wetting, -defoami-ng,thickening, coloring, rand plasticizing functions.

A preferred formulation for a coating material for single coatapplication to graft fiber board comprises the following in parts byweight:

Example l Iarts by weight Component Function Liquids Solids Water 80Base uid carrier.

Polyp)hosphate (water solu- 2.6 4 Wetting agent.

tion

Calcium stearate Slurry stabilizer. Carbon black (water disper- 4.0 0Coloring and cleavage.

sion). Green slate Tale (325 mesh) In the formula of Example I, thewater acts as a carrier for the solids and the polyphosphate and calciumstearate dissolve in the Water, the resin binder emulsifies in thewater, and the carbon black, green slate, talc and mica comprisediscrete solid particles in the slurry, suspended in the water. Theamount of water is, of course, variable to provided a more dense or lessdense slurry, with more or less liow, as required in the particularmethod of applying the coat, and as may be appropriate to drying timeand method, although sufficient water should be included to carry thesolid particles in free suspension. Ihe water dries from the finishedcoating, and in the slurry the water serves primarily as a medium forretaining the other materials in mechanically spreadable form orcondition.

The amount `of polyphosphate is governed primarily by the amounts yandnature of the solid particles which must be wetted to provide asuspension. Accordingly, in Example I, sufficient polyphosphate isincluded to insure wetting of the carbon black, green slate, talc andmica particles. It should be understood that in the preparation ofslurries in accord with this invention only a sufficient amount ofwetting agent should 'be employed to decrease the surface tension of thewater to the point at which substantially Iall of the solid particlesbecome wetted. The polyphosphate wetting agent actually employed in theformula of Example l was `a mixture off hexametaphosphate andheptametaphosphate, but sodium hexametaphosphate, sodium salt of alkylaryl sulfonate plus sulphate, polyhydroxyaloohol, ammonia, and certainsulphates and phosphates of higher synthetic alcohols have been foundentirely satisfactory when used alone, or in combination of two or more,in approximately equivalent quantities, that is, quantities that provideapproximately the same reduction in surface tension of the solution.Since certain grades and :sizes of the solids employed in the formulamay be more or less difficult to wet, it is appropriate to increase ordecrease the amount of wetting agent accordingly as is Well known in theart. It will be understood that the wetting agents mentioned aretypical, and that these or other wetting agents cornpatible with theother materials of the slurry may be employed as desired in the formulaof Example I and in the slurries hereinafter specified.

The carbon black provides coloring which is particularly appropriate inthe packaging of asphalt or Aother black or nearly black materials. Ithas been found also that carbon black 'assists the internal cleavageaction of the coating, and if carbon black is omitted, as, for example,when a black color is not desired, it maybe found desirable slightly toincrease the :amount of one or more of the other cleavage solids, suchas the green slate, talc or mica. Alternatively, if increased blacknessof the coating is desired, the quantity of Acarbon black may beincreased and the quantity of one or more of the yother cleavage solidsmay be accordingly slightly decreased.

Economic considerations dictate that no more than the minimum amount ofcarbon black be employed to provide the necessary coloration, andeconomics may further require that some of the blackening function beperformed by graphite, preferably in the form of small flakes of theorder of 325 mesh. Thus it has little effect on the action of thecoating if graphite fiakes are substituted for part or all `of thecarbon black, or even if up to a few parts of graphite are substitutedfor a minor portion of one or more of the cleavage solids. A specificformula comprisin g substantial amounts of graphite and bentonite clay,for example, is given hereinafter in Example II.

The internal cleavage function yis obtained primarily 4because of theinclusion in the coating of what are herein referred to as cleavagesolids, and these solids in the above `formula comprise green slate,mica and talc, although, as explained, the cleavage function 4is furtherraided by the carbon lblack and would be aided by any added orsubstituted ake graphite.

While the use of talc in release coatings has been previously suggested,the function of the talc in the present invention differs from that inprevious proposals. Mica has been employed heretofore in certain waxcoating formulations to increase the viscosity of the wax and to bridgeover pores in the wax film. The primary functions of the muscovite mica(as distinguished from -phlogopite mica, for example, which has adifferent chemical structure and crystalline shape) in the presentrelease coating, however, a-re to provide heat insulation and internalcleavage or lm splitting characteristics. Unexpectedly superior resultshave ybeen obtained with coatings comprising a high proportion of cheapgreen slate, which it has been found functions to assist the cleavagecharacteristics and the heat insulating characteristics 0f the mica andtalc, while permitting a substantial reduc tion of the amounts ofrelatively costly talc and mica. The inclusion of green slate in thecoating formulations herein described makes unnecessary the inclusion ofthe relatively much more expensive clay heretofore employed in manyrelease coatings in relatively large proportions to give body andspreadability to the coating slurry. it has been found important thatthe amount of sand, even in `finely ground state, be maintained at aminimum in the coating, since even a very small percentage results inrapid ysettling out of the particles suspended in the slurry, therebyseriously reducing the internal cleavage of the resulting coating, andsince small quantities of sand further result in severe erosion of thecoating equipment. Sand-free clay is, of course, much more costly thanthe usual commercial grades. It is possible to formulate excellentrelease coatings, however, which contain sand` free clay to replace afew parts of any one of the three primary cleavage solids of the formulaof the above table.

The theory of many prior release coatings has been to provide a coatingto which the packaged material, such as resin, asphalt, or latex, willnot adhere. The coatings of the present invention, however, are designedto adhere to the packaged material, at the upper face of the coatingfilm, and to adhere strongly to the container wall at the undersurfaceof the film. Release action is obtained by cleavage within the filmitself.

Unlike previous release coatings, the binder employed in this inventionis both bendable and tacky after drying and after completion of anypolymerization. The tack characteristics of the coating of Example I areimparted by the lacrylic resin, and a resin should be selected whichexhibits tackincss at temperatures above about F. to F. but which haslittle tackincss below such temperature. A coating having the mentionedtackincss characteristics can be applied to the fiber board and driedthereon and the board may then be rolled without appreciable resultantsticking together of the turns of the roll, but when the container isformed and hot asphalt is introduced into the container, the coating israised in temperature by the asphalt above the temperature at which thecoating exhibits suflicient tackiness to adhere to the asphalt.

To prepare a coating composition in` accord with the formula givenabove, the wetting agent or `agents are first added to the proper amountof water, with slow agitation, and the carbon black is next added. Withthe addition of the green slate, mica and talc, the speed of theagitator is increased to between about 600 to 1000 rpm. for a commercialagitator, thereby to provide thorough mixing and smooth consistency.Finally the binder material is added with continued high speedagitation. A certain amount of foam is normally to be expected and thisfoam is preferably reduced or eliminated 'by spraying with antifoamingagents, such as a sulfonated oil or a naphtha. The amount ofanti-foaming agent required will be negligible, has been found not toaffect the final coating in any noticeable way, and its use is advisableonly for making the handling of the slurry more convenient and toeliminate the waste and extra handling which would otherwise result frommechanical removal of the foam.

Coating material prepared in the specified manner in accord with theformula of Example I was spread by flowing on the upper surface of -alength of corrugated kraft fiber board, the board being fed under aIwiper roll to limit the coating thickness. The coating materialthickness was such as to contain substantially 8-10 pounds dry weight ofmaterial per one thousand square feet of coated surface. After dryingfor approximately two minutes at 300 F. and conditioning `at 72 F. at50% relative humidity for two hours, the coating solids were measured,the coated fiber board was formed into containers and the containerswere filled with Idead-level asphalt at about 400 F. The filledcontainers were then held for two hours at 250 F. and thereafterpermitted -to cool. At attnospheric temperatures thereafter thecontainers were torn away from the solid asphalt blocks which had formedinside. The fiber board came away readily and completely from theasphalt andthe inner surface of the container walls was found to bestill covered hy `a film of the coating. Even at corners of thecontainer, no fibers of the kraft .paper board had become adhered .tothe asphalt. The surfaces of the asphalt block were a dull very darkgray, almost black, indicating that a portion of the coating had becomebonded to and remained on the asphalt.

It is believed, from the results of tests, from microscopic examinationsand from theoretical analysis of the facts developed from the studies oflthe present and other coatings, that the muscovite mica which isincluded is primarily responsible for the excellent internal cleavagecharacteristics of the coating film 6. It is also clear that Itheacrylic resin binds the coating securely to the ber board surface andtends to strengthen the surface by impregnation of the fibers, and thatit causes adherence of the lm surface 6 to the lasphalt or otherpackaged material. Muscovite mica comprising very small plate-likeparticles so reduces the internal strength of the coating film that thelm may be cleft between its inner and outer surfaces. This cleavageaction is aided appreciably by the inclusion of green slate as one ofthe solid components, although it would be expected that green slate,like sand, would greatly reduce the cleavage or release characteristics.It has been found that the amount of .green slate may not greatly exceedapproximately the combined amount of mica and talc without-somereduction of desired cleavage characteristics. Green slate may beintroduced up to approximately 70% ofthe total solids weight if thepercentage of muscovite mica is maintained at at least 14% to produce auseful coating with good cleavage action. The introduction of greenslate np to about 40% of the total weight of the total solids insuspension permits some reduction in the -amounts of much more costlytalc required, thereby providing a substantial reduction in over-allcosts over a coating with a high percentage of talc. Reduction in theproportion of talc may also be accomplished by the substitution ofcertain types of sand-free clay, and it has been found that the use of akaolinite type of clay comprising particles in the form of flat platedcrystals, such as that mined near McIntyre, Georgia, and sold by EdgarBrothers Company of Mc- Intyre, Georgia, as type ASP 900, having aparticle size of about 2 micron, when used to replace part `or all ofthe green slate, permits a reduction in the amount of talc and a slightreduction in the amount of mica below the proportions given in ExampleI, as is more particularly exemplified hereafter in specic formulas.

The talc, green slate and mica yall contribute to the heat insulatingproperties of the film, which resulted in the avoidance of any damage tothe fiber board in the hereinabove described experiment from 400 F.asphalt, for example. The green slate and talc seem to become orientedbetween plates of mica in a manner such that the heat insulationobtainable is comparable to that of a coating of equal thickness, and ofthe same total solids content, but in which mica was substituted for thetalc and green slate.

Example II As a second example of a single release or cleavage coatingmaterial, a slurry may be prepared as outlined above having thefollowing formula:

A third exemplary formula for a single coat material embodying thisinvention is as follows:

Example III Parts by Function weight Water Carrier. Sodium alkyl arylsulfonate 3 Wetting agent. Sulfonated oil 1 Anti-foam.

Green slate 60 Filler and cleavage. Washed clay (AS 90 30 Do. Color 3Color, Mica 22 Cleavage. Butadiene-styrene copolymer 1l Binder.

' Stabilizer.

Soap 1 It will be seen that the two formulas last set forth includesomewhat less mica than the iirstformula, and that in each laterinstance a different binder resin is specified.

Thoroughly satisfactory results are obtained with the slurries ofExamples II and III spread and dried as described above at a rate toforma coating of between 6 to about `12 or 14 pounds dry weight,l ofsolids per 1000 square feet of coated container wall surface. It will beseen, accordingly, that the m-inimumI weight of mica per 1000 squarefeet in a coating comprising between 7 and 8% of mic-a would beapproximately 0.45 or 0.50 pound. More economic and higher qualitycoatings comprise from about 12% mica to 20% mica, giving labout onepound of mica per 1000 square feet of surface. As herein explained, thepercentage of mica which can be employed with good results reaches amaximum practical limit of approximately 40%, and a coating of 12 or 13pounds per 1000 square feet might, accordingly, comprise about 5 poundsof mica per 1000 square feet.

While coatings thicker than 12 pounds per 1000 square feet would beoperative, economics dictates that the coating thickness should be nomore than at this rate but should be as thin as experience may proveacceptably operative. Since from about 60% to 92% of the total solidsweight may be cleavage, filler or release solids other than mica, thetotal weight per 1000 square feet for these materials may range fromabout 3.5 pounds to about l2 pounds.

For hot dead level asphalt the coating is generally somewhat thickerthan `for mopping -asphalts, depending largely on the maximumtemperatures involved. Thus, while a coating of only 3 or 4 pounds per1000 square feet might suice if the coating contains at least about 14%mica for materials poured into `the container at 175 F.200 F., deadlevel asphalt introduced at 375 F., for example, would require a minimumof labout 8 or 10 pounds per 1000 square feet and the formula for thecoating should comprise somewhat more than 8% of mica and should furthercomprises a resin which is not destroyed when heated to the region of375 F. to 400 F. Double coats as described herein are generallypreferred to single coats in high temperature dead level asphaltpackaging.

While approximately 10 parts of resin emulsion is specified in each ofExamples I, II and III, the parts of resin may be substantiallyincreased, for example, to about parts, without thereby reducing theeffectiveness of the coating. Increasing the parts of resin binder aboveabout 10 parts may be found necessary or desirable to reduce any flakingof the coating which may be encountered.

The Mineralite mica of the muscovite type as employed in the coatingcompositions of this invention should be of very line mesh.Specifically, excellent heat insulation and cleavage characteristics ofthe coating and good spreading characteristics of the slurry areobtained with 1000 mesh mica, but appreciably less readily spread andless stable slurries and less effective coatings result from the use ofmica having particle sizes greater than sizes corresponding to 325 meshand particles as large as 250 mesh are not suitable, best results beingobtained with particles of about 1000 mesh or smaller, such as 3000mesh.

The Mineralite mica of the muscovite type is characterized by the factthat its individual particles are of a scale-like crystalline shape. Itis believed that this physical characteristic is closely tied in withthe excellent cleavage characteristics exhibited by the coatings underdiscussion. The chemical analysis of these mica flakes A specific micawhich has proved highly satisfactory is mined near Kershaw, SouthCarolina, `and sold by Mineralite Sales Corp., 90 yPine Street, New York5, N.Y., as -Mineralite 4X (1,000 mesh), Mineralite 3X (325 mesh) andMineralite 5X (3000 mesh). Such mica is within the chemical requirementsgiven above.

'Ihe clay Iprovided in Examples II and Ill is of the flat plated crystaltype such as is found at and mined near McIntyre, Georgia, and which iscommercially available as Edgar Brothers Company, Metuchen, NJ., typeASP-900 (2 micron size particles) and type ASP 400 (3 micron sizeparticles). Example II shows the use of 80 parts of clay and only 9parts of mica. It

has been found, as will be understood from a comparison of this examplewith others given herein, that this clay is superior to talc or othercleavage or filler materials in making the mica effective in thecoating, both as to cleavage and heat insulating properties, and, whileclay alone, without mica, does not provide the desired results, theamount of mica may be substantially reduced with use of substantialamounts of iiat plated crystal clay and ake graphite without therebyappreciably adversely affecting the action of the coating. In ExampleII, mica comprises only about 8% of the total solids. Because ofeconomic considerations it is not practical to decrease the amount ofmica to this minimum percentage, and better results are obtained and aless costly coating can be prepared if mica is included at not less than10% or 12% of the total solids.

Green slate, sometimes called mineral stabilizer, useful in thisinvention comprises that mined near Fairmont, Georgia, of 325 mesh andsold by F. I. Funkhouser & Company, 138 W. Washington St., Hagerstown,Md.

Suitable tales are those of 325 mesh mined near Chatsworth, Georgia, andsold by Whittaker, Clark and Daniels, 260 Broadway, New York, 13, NY.,as No. 1648 and No. 1767, and those mined near Alpine, Albama, and soldby Whittaker, Clark and Daniels, as Clatal Tale No. 2952 and No. 2953,the last mentioned, however, being of 200 mesh and somewhat lessdesirable in this invention.

Graphite No. 1132 sold by Jos. Dixon Crucible Co., Wayne & MonmouthStreets, Jersey City 3, NJ., is a commercially available 325 meshgraphite, and graphite No. 6580 is a 425 mesh graphite obtainable fromthe same source, each of which is adapted for use in this invention.

A carbon black which has been found suitable is that sold by Binney &Smith Company, Inc., of 380 Madison Ave., New York, N.Y., as Aqua BlakG, while Black B Paste sold by General Dyestutf Company of 2459Wilkinson Blvd., Charlotte 1, N C., is a satisfactory black pigment. Inthe several specific exemplary formulas herein set forth, severaldiiferent wetting agents, anti-foam materials and stabilizers arementioned, together with ranges of substitutes therefor. Such materialsgiven in one formula may generally be substituted in the other formulas,although in slightly varying amounts depending upon the difficulty ofwetting certain of the components, for example, although it will also beunderstood that ammonia should not be used as a wetting agent if thesynthetic resin binder t0 be employed is incompatible with ammonia.Furthermore, it will be understood that the binder materials specifiedin any one formula may be substituted from one to another of theformulas in a single coat process. Particularly useful as the resinbinder in any of the above examples are resin emulsions of the typecomprising acrylate and methacrylate resin materials together withsufficient lower alkyl polyacrylate materials to provide tackiness inthe final coat for temperatures above about to 170 F., but with thepolyacrylate limited in amount whereby the coating is not tacky belowthe specified temperature. Also useful and satisfactory arebutadiene-styrene copolymers, having relatively high butadiene contentto provide tackiness of the coating above about F.

Somewhat to be preferred to the single coat film described hereinaboveand shown in FIG. 2 is a double coat film as shown in FIG. 3 wherein thebase coat composition applied to the fiber board, or other containermaterial, comprise muscovite mica suspended in an aqueous emulsion of abinder material, such as an acrylic resin, in which mica alone mayprovide vthe release or cleavage characteristics, or in which up to amajor portion of the mica may be replaced with a clay, bentonite,fullers earth, lampblack, talc, green slate, carbon black or graphite,or a combination thereof. In accord withI this invention, a base coat soconstituted, as more particu larly set forth hereafter, may provideinternal cleavage satisfactory for the release function, but it has beenfound -that the base coat may be much reduced in thickness, or in weightof solids per square foot of surface, by covering the base coat with atop coat 9 comprising a tough, flexible and pliable plastic materialiilm. Suitable materials for this top film are vinylidene chloride-vinylchloride copolymers, or acrylic-methylmethacrylate copolymers, or highstyrene butadiene-styrene copolymers, or vinylidenechloride-acrylonitrile copolymers, as more particularly discussedhereinafter. The top film is preferably applied in emulsion form, andthe emulsion preferably includes a thickening agent in suspensiontherein for the purpose of increasing the ease of handling.

Base coats 8 of a double coating may be generally similar to the singlecoats `6 provided in Examples I, II and III above. The followingspecific examples of base coat formulations have proved highlyeffective.

Example IV The preparation of this emulsion slurry is as described inconnection with Example l, and an anti-foaming agent, as before, may beused in the course of mixing.

A base coat formulation yielding comparable excellent results is asfollows:

Example V Parts by weight Component Function Liquids Solids Water 90Carrier. Polyphosphate. 1. 76 0. 24 Wettmg agent. Protein dispersion.4.1 0.9 Stabilizer. Lampblack 4 Coloring and cleavage. M" 35 Cleavage.Green slate (600 mesh). 80 Cleavage and filler. .Acrylic resin 6 4Binder.

In the above Example V, in place of the 35 parts of mica and 80 parts ofgreen slate, one may use 25 parts of mica, 25 parts of talc (425 mesh)and 67 parts of green slate, or one may use 35 parts of mica and 65parts of talc.

As a further alternative the base coat formulation may comprise theparts of water, wetting agents, calcium stearate and resin binderspecified in Example IV and Example V, but with 22 parts of carbon blackdispersion (l1 parts of carbon black in l1 parts of water) and 55 partsof mineralite mica (1000 mesh). Since carbon black and muscovite micaare more expensive than talc or clay, and much more expensive than greenslate, it will usually befound desirable to include at least 60 parts ofgreen slate, and, in order to insure maintenance of the excellentcleavage characteristics, to include a minimum of approximately parts,or 412%, of mica.

Excellent cleavage characteristics of coating 8 are maintained withincreased parts of muscovite mica in the formulas of Examples IV and V,with reduction of the parts of other solid constituents, but anoticeable and undesirable tendency of the mica to thicken the slurry toa dough-like consistency occurs when the proportion thereof is increasedto more than approximately 40 parts,

or to more than approximately 40% of the total solids. The nature of thesolids used may make possible slightly greater proportions of mica. Forexample, substantial increase in the amount of lampblack or carbon blackmay permit somewhat higher percentages of mica, but since lampblack andmica are high in cost, no practical purpose would be served by suchincrease in the amounts of these components. In formulations in accordwith this invention, the maximum permissible percentage of muscovitemica to total weight of solids may, accordingly, be considered asapproximately 40%, whereas the minimum percentage of the mica to obtainthe cleavage action is substantially 7% to 8%. Lower percentages ofmica, below approximately 17%, have been found to necessitate theinclusion of substantial amounts of costly graphite, carbon black, ortalc, or combinations thereof, to replace, for example, the relativelyinexpensive green slate, although it has also been found that greaterpercentages of ASP 900 clay may also permit reduction of the percentageof mica to approximately 12% or 14%. Example II gives a formula withkapproximately 8% mica, but with high proportions of ASP 900 clay andgraphite, whereas Example lll, with 18% mica, 52% green slate, 26% clayand 3% color, such as lampblack, and with no graphite, providesexcellent cleavage characteristics with total solids costs considerablyreduced. `lt has also been found that insuiiicent heat blockingcharacteristics of the coating result from the use of less than about10% of mica and completely satisfactory heat blocking requires about 14%or more of mica, in percentage of the total solids, unlessunecoriomically large percentages of clay or other expensive materialsare employed.

Further specific examples of slurry compositions which are adapted forspreading on a container wall to form either a base coat for a doublecoat cleavable coating or a single cleavable coat are as follows:

Example VI Filler and cleavage.

Clay (ASPQOO)- 40 Muscovite mica 34 Cleavage. Calcium stearate l.Stabilizer. Butadiene-styrene copolymer emul- 20 Binder.

sion (Dow 512K) (48% resin).

l Solid weight.

In Example VI, the butadiene-styrene copolymer should be of the typehaving lower styrene percentages, that is, a styrene-butadiene ratio of`6 4 or 5.5-4.15. In the example given, the resin emulsion which isadded forms a finished resin after setting and drying weighing 48% ofthe emulsion. As in the other examples given herein, the materials arelisted in the preferred order of addition to the mixing vat, water beingiirst placed in the vat and the remaining materials being thereafterintroduced and mixed in the order indicated, although the order may bevaried as desired. The wetting agents of Example VI will comprise,preferably, as added, a few parts of water, as may several otheringredients, whereby the final slurry may comprise some or 100 parts ofwater. The amount of Water may vary in different applications to producea slurry of the desired ow characteristics for coating the specificcontainer material with a coating of the desired thickness using thespecific coating machine available. The amount of water specified issuiiicient to suspend, -dissolve and emulsify the specified quantitiesof the materials, however, and is appropriate to provide a slurry ofsubstantially the correct spreadability for application to kraft paperboard by means of a wiper roll spreading machine.

Example VII Parts by Function weight Water 80 Carrier. Polyphosphate l0.1 Wetting agent. Sodium alkyl aryl sulfonate.- 1 0.3 Do. Clay (ASPQOO)70 Filler and cleavage. Green slate 14 Do. Graphite 20 Coloring mdcleavage. Muscovite mica 14 Cleavage. Calcium stearato 0.5 Stabilizer.Acrylic resin emulsion (40%) (Rohm l0 Binder.

& Haas IVN-80).

l Solid Weight.

Example VIII Parts by Function weight Water 80 Carrier. Polyphosphate 0.l Wetting agent. Polyoxethylene ether 0. 5 Do. Carbon blacl-: 4Coloringr and cleavage. Green slate 65 Filler and cleavage. Muscovitemica.. 34 Cleavage. Calcium stearate. 1 Stabilizer. Acrylic resinemulsion (40%) (Rohm l0 Binder.

& Haas WN-80).

Several types of plastic or latex compositions have been found to beuseful in base coat formulations for a double coat process and, ingeneral, these types are useful in preparing a slurry for single coatapplication.

Specifically, in the single coat formulations of Examples I, Il and III,and in the base coats of Examples IV and V, the binder material maycomprise acrylic resins, such as polymerizcd acrylic acid, methylacrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, ormixtures thereof, or other polymerized acrylic resins of similarcharacteristics. The lower alkyl polyacrylates are generally softer thanis desired, and polymethylmethacrylates are preferred. Binders havingthe desired characteristics for use in bottom or base coat formulationsand for use in single coat formulations, may be prepared by thecombining of an acrylate or methacrylate resin with sucient lower alkylpolyacrylates to provide a coating which exhibits tackiness attemperatures above about 170 degress F., but which, at lowertemperatures, possesses the characteristic hardness of acrylate resins.As later explained acrylic-methylmethacrylate copolymers form suicientlyhard films to be useful as top coats in a double coat application.

Single coats and base coats, in Examples I, II, III, 1V and V maycomprise an acrylic resin combined with any of several other types ofresins. Specifically, l part of a lower alkyl polyacrylate with parts ofacrylonitrile-methacrylate copolymer is suggested in Example Il, andVinylidene chloride-acrylonitrile copolymer is useful with plasticizersselected to reduce the film hardness. Care should be taken, however,that 4the plasticizer does not cause the material to be -destroyed bythe temperatures of the material to be packaged. On the other hand, 4parts of Vinylidene chloride to 1 part of acrylonitrile copolymer withlittle or no added plasticizer provides an excellent hard top coat.

Examples of acrylic resin copolymer and polyvinyl acetate copolymeremulsions which are commercially available and are suitable for bottomcoats or single coats are AC-33, WN-77 and WN-SO manufactured by Rohm &Haas, Washington Square, Philadelphia 5, Pa. These emulsions may beemployed with plasticizers to provide suicient softness and tack forbottom or single coats, but the AC-33 is suiciently soft and tackywithout Vany added plasticizer, while the non-ionic acrylic resinemulsion WN-80 and polyvinyl acetate emulsion WN-77 may be used as thetop coating material. Walpol-9301 supplied by Reichold Chemical Co.,Inc., 525 N. Broadway,

12 White Plains, N.Y., is a polyvinyl-acetate homopolymer which providesa satisfactory base or single coat. This material should be combined,however, with a plasticizer to reduce brittleness and impart tackiness,for temperatures of about F. and above, such as dibutylphthalate orother compatible tacky alkyd resins.

It is important to control and limit the amounts of alkali salts in theslurry when using acrylate, methacrylate and some other acrylic resins,since it has been found that swelling of the resin may occur, and that agel may be formed in the slurry, and, further, that a very soft film mayresult. Thus 4the mica, talc, clay, slate and other ingredients shouldbe selected to comprise a minimum of alkali salts.

Example lll indicates that butadiene styrene copolymers are useful insingle coats, and it has been found that they are also useful in base orbottom coats and in top coats. Top coats require materials of the higherstyrene percentages, i.e. more than 60% styrene, but materials of lowerstyrene percentages, such as Plio 101A, Plio 102 and Plio 160, which areapproximately 40% to 45% butadiene- 60% to 55% styrene emulsionssupplied by Goodyear Tire and Rubber Co., 1144 E. Market Street, Akron16, Ohio, are well adapted for use in bottom or single coats. 40%butadiene-60% styrene emulsions, as exempliiied by S12-K and 5l2-R ofDow Chemical Co., Midland, Mich., are satisfactory as bottom or singlecoats, as are the Chemigum 236 and Chemigum 246 butadiene-acrylonitrileemulsions of Goodyear Tire and Rubber Co.

Top coats 9 exhibiting desired characteristics include, in general, theresins previously mentioned. More speciically, suitable top coat resinsare vinyl chloride, such as Pliovic 300 supplied by Goodyear Tire andRubber Co., vinyl acetates, and vinyl chlorides, which polymerize toform suitably hard, non-tacky top coat films. If the lms formed of anyof these resins are too brittle in the specic application, appropriateplasticizers may be added.

In the case of the specific exemplary commercial product Pliovic 300,the vinyl chloride should be polymerized in the presence of a catalystto form a latex or resin prior to emulsiiication, and a highly effectivetop coat material comprises a high proportion, Le. 60%-65%, of vinylchloride, with a relatively low proportion (40%- 35%) of Vinylidenechloride, plasticized with a modified polyacrylate. Excellent resultsare obtained with X-2l02 emulsion supplied by Dow Chemical Co., anemulsion of from about 50% to 35% Vinylidene chloride, with 50% to 65%vinyl chloride. Polyvinyl acetatevinylidene chloride copolymers are alsosuitable for top coats. Vinylidene chlorides provide medium hard films,and are most satisfactory as a top coat when mixed with a hardermaterial, such as, for example, a vinyl material. Copolymers ofpolyvinyl acetate-acrylonitriles and of Vinylidenechloride-methylmethacrylates form suitably hard lm top coats, whileacrylonitriles alone, which polymerize naturally, may be employed, asmay polyvinyl acetates of low molecular weights. A commercial example ofa suitable polyvinyl acetate is Rohm & Haas WN-77 emulsion, which it isbelieved, comprises, with the acetate, an acrylate copolymer.

With respect to the use of vinyl chloride-Vinylidene chloride resins incoatings in accord with this invention, it has been found that 50% to70% vinyl chloride to 50% to 30% of Vinylidene chloride is an acceptablerange for top coatings. The vinyl chloride tends to impart toughness orhardness and tensile strength to the lm, while more Vinylidene chloridetends to increase the ease of spreading at lower temperatures andincreases the water resistance and tack of the nal coating. A top coatof not more than 40% Vinylidene chloride may be suitably plasticizedwith chemical and polymeric plasticizers such as tri-ethylene glycoldi-2 ethylbutyrate, or with lower styrene butadiene-styrene copolymeremulsions, or with water-soluble plasticizers with high evaporativetendencies. In the last mentioned case, the heat of drying of the iilmfacilitates evaporation and subsequent fusion of the copolymer. Examplesof such soluble plasticizers are alcohols, such as glycerol or ethyleneglycol, or their derivatives such as diethylene glycol monoethyl etheracetate. Approximately to 35 parts of the 100% plasticizer to 90 to 65parts of the vinyl chloride-vinylidene chloride copolymer is generallyappropriate.

In certain cases, it may be found desirable to harden the film andreduce its tackiness by the addition of a urea formaldehyde type ofresin. Such addition might be desired, for example, with vinylchloride-vinylidene chloride copolymers wherein the vinyl chloride is inthe range of about 50%.

Vinyl chloride-vinylidene chloride may form a suitable base coat orsingle coat if plasticizer, for example, with synthetic latex.

An acetate resin material useful as a top coat is sold by Rohm & Hass asWN-77, and such material is exemplary of polyvinyl acetate-acrylatecopolymers which form good top coats and which may, with suitableplasticizers, be used in a single coat or base coat formulation.

The high styrene butadiene-styrene copolymers, such as Pliolite 170furnished by Goodyear Tire and Rubber Co. which comprises approximately30% butadiene and 70% styrene, are useful either alone, or with otherresins, as top coat materials.

Polyethylenes of molecular weights between about 1500 and 6000 may beemulsiiied for use in top coats, although polyethylenes of highermolecular weights are not readily emulsiable. Obtainable from SemetSolvay Petrochemical Division, Allied Chemical and Dye Corporation, 40Rector Street, New `York 6, N.Y., are solid polyethylenes AC-6(molecular weight 2,000), AC-7, AC-617 (molecular weight 1,500) AC-6l5(molecular weight 5,000) which may be emulsiiied and which are useful astop coats.

Vinylidene chloride, 4 parts, to l part acrylonitrile copolymer,acrylic-methylmethacrylate copolymers, vinylidene,chloride-methylmethacrylate copolymers, and acrylonitrile are alsouseful as top coats.

While each of Examples VI, VII and VIII provide when applied an operablesingle coat on the container wall, a superior coating for the wallresults from the application of a top coat to cover such single coat. Atop coat emulsion for spreading on a base coat formed from the slurry ofany one of Examples I through VIII, but which is particularly applicableto the base coating formed by the 'slurry of Example VI, comprises, asExample Vl(a), 250 parts water, 6 parts of starch, 1.5 parts sodiumalginate, and 100 parts of 50% emulsion of vinylidenechloride-acrylonitrile copolymer. In this top coat mixture, the starchand the sodium alginate function only to thicken the mixture for moreeffective spreading, and neither of these materials perform any usefulfunction in the finished coat. Upon kfilling a container so coated withhot dead-level asphalt it seems probable that the two thickening agentsare destroyed, but whether or not destroyed, the top coat bondssatisfactorily to the asphalt and the base coat cleaves in the desiredmanner. Hence the small amount of starch present does not in any wayValter the cleavage function.

A top coat formulation specifically appropriate for application over abase coat formed from Example VII, but useful with the other base coats,if desired, comprises, as Example Vll(a), 250 parts water, 1.5 partssodium alginate and 100 parts .polyvinyl acetate emulsion (Rohm & HaasWN-77).

A top coat mixture generally useful but specifically adapted forapplication to a base coat formed from Example VIII is as follows,Example VIII(a), 250 parts Water, 6 parts starch, 1.5 parts sodiumalginate, and 100 parts acrylic resin emulsion (40%) (Rohm & Haas 14WN-SO). As in Examples VI(a) and Vll(a), the starch and sodium alginatehave no function in the iinished coating.

It will be understood that the resins herein mentioned as useful forsingle coats and for base coats are employed as binder materialsemulsied in the slurriers containing suspended solids. The top coats asdescribed herein may comprise a resin alone, without suspended solids.The top coats are preferably spread in emulsion form on top of thealready formed and preferably dried or set bottom coat. It is practicalwith resins adapted for spraying, however, to apply the top coat by thismethod, rather than by a owing on of an emulsified resin, and otherknown methods of applying resin surface films could be employed ifdesired. As further indicated by the above examples, it is contemplatedthat various t-hickeners or other materials which have no function inthe finished top coat may be utilized to provide an appropriate body topermit ready application of the top coat with the type of coatingequipment to be used.

While the formulations and modifications thereof discussed above areintended for application by flowing the slurry onto a iiber boardsurface, to be smoothed, spread and limited in thickness by a wiperroll, it will be apparent to those skilled in the art that the viscosityof the slurry should be varied in accord with the desired method ofapplication. A thicker material, for example, may be desired for brushcoating, while a thinner material may be required for spray coating.Thinning is readily accomplished by the mere use of additional parts ofwater, and possibly by .a slight increase in the `amounts of wettingagents and of the calcium stearate. When the mixture is to be madethicker, however, further precautions are necessary to insure, with areduction in the amount of water, that the solids will remain insuspension in the slurry.

While only certain preferred embodiments of this inrvention have beenshown and described by Way of illustration, many modifications willoccur to those skilled in the art and it is, therefore, desired that itbe understood that it is intended in the appended claims to cover allsuch modications as fall within the true spirit and 'scope of thisinvention.

thetic resin binder material bonded to said wall, and furthercomprising, dispersed in said binder material, solid particles ofbetween 200 and 3000 mesh of a material selected from the groupconsisting of clay substantially only of the kaolinite type, fullersearth, lamp black, liake graphite, green slate, carbon black and talcand mixtures thereof, said binder material being a anember of the groupconsisting of polymerized acrylic acid, polymerized ethyl acrylate,polymerized methyl acrylate, polymerized methyl methacrylate,polymerized ethyl methacrylate `and copolymerized mixtures thereof, andacrylonitrile-methacrylate copolymer, butadienestyrene copolymer,vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinylchloride copolymer and polyvinyl acetate, and mixtures thereof, thesolids content of said resin binder being present in proportions byweight between about 37.5% of the total solids content of the namedsubstances Vand said mica being present in proportions by weight betweensubstantially 7-40% of the total solids content of the named substances.

2. The container of claim 1, in which said resin binder is an acrylicresin.

3. A container for -hot dead level asphalt or the like having a wall theinner surface of which is protected by a sand-free cleavable coatingconsisting essentially of muscovite mica particles of between about 300and 3000 mesh dispersed in an acrylic resin having sucient lower alkylpolyacrylate and higher alkyl acrylate copolymers incorporated thereinto provide a tacky surface at temperatures above about 170 F. and asubstantially nontacky surface below about 170 F., and furthercomprising dispersed solid particles of between 200 and 3000 mesh of amaterial selected from the group consisting of clay substantially onlyofthe kaolinite type, fullers earth, lamp black, flake graphite, greenslate, carbon black and talc and mixtures thereof, the solids content ofsaid resin being present in proportions by weight between about 3-7.5%of the total solids content of the named substances and said mica beingpresent in proportions by weight between substantially 7-40% of thetotal solids content of the named substances.

4. A fiber board container for dead-level asphalt or the like having awall the inner surface of which is protected by a substantiallysand-free cleavable base coat consisting essentially of a polymerizedorganic resin which is tacky at normal atmospheric temperatures andsolid particle cleavage constituents comprising between substantially740% by weight of plate-like shaped mica particles of particle sizebetween substantially 300 and 3000 mesh, said resin being selected fromthe group consisting of polymerized acrylic acid, polymerized ethylacrylate, polymerized methyl acrylate, polymerized methyl methacrylate,polymerized ethyl methacrylate and copolymerized mixtures thereof, andacrylonitrile-methacrylate copolymer, butadiene-styrene copolymer,vinylidene chloride-acrylonitrile copolymer, vinylidene chloridevinylchloride copolymer and polyvinyl acetate, and mixtures thereof, thesolids content of said resin being present in proportions by weightbetween about 3-7.5% of the total solids content of said resin andcleavage constituents combined and said wall being further protected bya top coat overlying said base coat and comprising a polymerized organicresin which is tacky at elevated temperatures of about 400 F. and aboveand which is substantially hard and non-tacky at temperatures belowsubstantially 150 F.

5. A double coated fiber board container for asphalt or the like whereinthe base coat on the inner surface of said fiber board consistsessentially of a heat resistant substan tially sand-free internallycleavable coating containing muscovite mica particles, a particulatematerial selected from the group consisting of tlake graphite, carbonblack, lamp black, clay substantially only of the kaolinite type,fullers earth, green slate, and talc, and mixtures thereof and a tackybinder selected from the group consisting of polymerized acrylic acid,polymerized ethyl acrylate, polymerized methyl acrylate, polymerizedmethyl methacrylate, polymerized ethyl methacrylate and copolymerizedmixtures thereof, and acrylonitrile-methacrylate copolymer,butadiene-styrene copolymer, vinylidene chlorideacrylonitrile copolymer,vinylidene chloride-vinyl chloride copolymer and polyvinyl acetate, andmixtures thereof, said mica being present in the form of particles of asize between 300 and 3000 mesh, the solids content of said tacky binderbeing present in proportions by weight between about 3-7.5% of the totalsolids content of the named substances and said mica being present inproportions by weight between substantially 7-40% of the total solidscontent of the named substances, and wherein the top coat is disposedover said base coat and consists essentially of an asphalt-adherent coatselected from the group consisting of polymerized acrylic acid,polymerized ethyl acrylate, polymerized methyl acrylate, polymerizedethyl polyacrylate, polymerized methyl polyacrylate, polymerized vinylchloride, polymerized vinyl acetate, polymerized vinyl alcohol,vinylidene chloride, acrylonitrile, polyethylene and polyvinyl acetateand copolymers thereof.

6. The container of claim 5 in which said top coat presents a tackysurface at temperatures above substantially 400 F. and presents asubstantially hard and nontacky surface at temperatures belowsubstantially F.

References Cited in the tile Vof this patent UNITED STATES PATENTS1,916,970 Denning July 4, 1933 1,983,349 Dreyfus Dec. 4, 1934 2,183,711De Witt Dec. 19, 1939 2,333,023 `Manor Oct. 26, 1943 2,396,633 BernsteinMar. 19, 1946 2,426,316 Martin Aug. 26, 1947 2,453,880 Vanderbilt et al.Nov. 16, 1948 2,494,920 Warrick Jan. 17, 1950 2,518,359 Mohrer Aug. 8,1950 2,525,071 Hardy et al Oct. 10, 1950 2,624,683 Bezman Ian. 6, 19532,626,941 Habeck Jan. 27, 1953 2,634,459 Irons Apr. 14, 1953 2,672,454Rother et al Mar. 16, 1954 2,704,105 Robinson et al Mar. 15, 19552,751,366 Braendle June 19, 1956 2,804,205 Barton et al Aug. 27, 1957OTHER REFERENCES Paint Manufacture, October 1942, XII, pp. 182-186.Paint Manufacture, December 1942, XII, pp. 224-225.

1. A CONTAINER FOR HOT DEAD LEVEL ASPHALT OR THE LIKE HAVING A WALL THEINNER SURFACE OF WHICH IS PROTECTED BY A SUBSTANTIALLY SAND-FREECLEAVABLE COATING CONSISTING ESSENTIALLY OF PLATE-KIKE SHAPE MICAPARTICLES OF BETWEEN ABOUT 300 AND 3000 MESH AND DISPERSED IN APOLYMERIZED SYNTHETIC RESIN BINDER MATERIAL BONDED TO SAID WALL, ANDFURTHER COMPRISING, DISPERSED IN SAID BINDER MATERIAL, SOLID PARTICLESOF BETWEEN 200 AND 3000 MESH OF A MATERIAL SELECTED FROM THE GROUPCONSISTING OF CLAY SUBSTANTIALLY ONLY OF THE KAOLINITE TYPE, FULLER''SEARTH, LAMP BLACK, FLAKE GRAPHITE, GREEN SLATE, CARBON BLACK AND TALCAND MIXTURES THEREOF, SAID BINDER MATERIAL BEING A MEMBER OF THE GROUPCONSISTING OF POLYMERIZED ACRYLIC ACID, POLYMERIZED ETHYL ACRYLATE,POLYMERIZED METHYL ACRYLATE, POLYMERIZED METHYL METHACRYLATE,POLYMERIZED ETHYL METHACRYLATE AND COPOLYMERIZED MIXTURES THEREOF, ANDACRYLONITRILE-METHACRYLATE COPOLYMER, BUTADIENESTYRENE COPOLYMER,VINYLIDENE CHLORIDE-ACRYLOONITRILE COPOLYMER, VINYLDENE CHLORIDE-VINYLCHLORIDE COPOLYMER AND POLYVINYL ACETATE, AND MIXTURES THEREOF, THESOLIDS CONTENT OF SAID RESIN BINDER BEING PRESENT IN PROPORTIONS BYWEIGHT BETWEEN ABOUT 3-7.5% OF THE TOTAL SOLIDS CONTENT OF THE NAMEDSUBSTANCES AND SAID MICA BEING PRESENT IN PROPORTIONS BY WEIGHT BETWEENSUBSTANTIALLY 7-40% OF THE TOTAL SOLIDS CONTENT OF THE NAMED SUBSTANCES.